1. Field of the Invention
The present invention relates to a battery structure for an electric vehicle.
2. Discription of the Related Art
Conventionally, high performance batteries having lithium Ion etc. as a main constituent, have been employed as batteries for an electric vehicle. However, since these high performance batteries exhibit relatively high caloric value in use, it has been required to enhance the cooling performance of the batteries.
From this point of view, a variety of battery structures for improving the cooling performance are disclosed in Japanese Patent Publications. For example, in Japanese Patent Publication No. 7-47892. Cylindrical batteries are interposed between two plates made of a highly conductive thermal material which is vertically oriented, i.e., from the upside and downside. The so-assembled batteries are fixed on a vehicle body through the plates so as to define air passages therebetween. Consequently, with the motorcar traveling, cooling air is introduced into hollow parts of the batteries and the air passages between the plates.
Disadvantages of the known battery structure included heat is apt to be stagnant in the air passages because of their narrowness, and when the batteries are oriented in the back and forth, or longitudinal, direction of a vehicle, the batteries are subject to irregular cooling effect along their axial length.
Another disadvantage of the known battery structure is that the batteries interposed between the plates are easy to displace in the axial direction. Even a buffer member is provided between the plates and the batteries to solve the displacement problem, the draft cooling capability of the battery structure is adversely affected.
In addition to poor cooling performance, because known battery structure having cylindrical batteries interposed between the two plates is fixed on the vehicle by fastening the plates to members on the vehicle's side, detaching the batteries from the vehicle becomes difficult.